Historically, candles served a functional purpose, but today they are further used to enhance decoration, aroma and ambiance. References to candles date back to at least 3000 B.C. in Crete and Egypt. Candle making as known today, began in the 13th Century. Candle molding machines were developed in the 15th Century. The braided wick was introduced in 1825. A continuous wicking machine was invented in 1834. Manufactured paraffin was introduced in 1850, providing an alternative to tallow. In 1854 paraffin and stearin were combined to create stronger candles, very similar to those used today. Through the past century, a number of “modern” technical innovations have been introduced to improve candle performance and production. Most of the focus has been towards advancing manufacturing methods (U.S. Pat. Nos. 3,964,858; 4,291,458; 4,830,330; 5,537,989; 5,927,965; 6,228,304), improved wick sustainers (U.S. Pat. Nos. 3,819,342; 4,332,548; 4,818,214; 5,690,484; 5,842,850; 5,961,318; 6,062,847; 6,454,561; 6,508,644), varying waxes formulations (U.S. Pat. Nos. 6,066,329; 6,342,080; 6,562,085; 6,599,334), and improving woven (i.e. braided) wick technology (U.S. Pat. Nos. 3,940,233; 4,790,747; 5,124,200). (The entire contents of all of the patents and other publications mentioned anywhere in this disclosure are hereby incorporated by reference in their entireties.)
Traditionally, a candle is made up of a single or multi combustible, porous core or wick surrounded by a fusible, flammable solid wax or wax-like material, such as absolute or blends of petroleum (paraffin) wax, mineral (montan) wax, synthetic wax (polyethylene or Fischer Tropsch), natural waxes (vegetable or animal) and clear candle waxes or “gels” (ETPA). Prior art shows candle wicks referring to cotton or cotton-like materials (i.e. rayon, nylon, hemp) woven, or braided and with or without a “self-supporting” core material such as metal, paper, cotton, polyethylene fiber or a stiffing agent. When a candle is lit, the heat from the flame melts the solid fuel and the resulting liquid then flows up the wick by capillarity. This liquid is subsequently vaporized, the middle zone of the flame is where the vapor is partially decomposed, and the outer layer is marked by combustion of the vapor and the emission of carbon dioxide, water and other vapors into the atmosphere. The wick is the pivotal component for a candle to burn. Although there have been improvements in candle systems and wicks over the past century, there are still complications, limitations and hazards associated with prior wick technologies.
In August 1997, ASTM Subcommittee F15.45 was formed to address candle fire safety issues and to set safety standards. The frequency of injuries associated with candles approximately doubled from the mid-1980s to the mid-'90s. They also reported that there had been an increase in the number of candle recalls due to fire safety issues, including excessive flames in gel, terra cotta and metal container candles and various other types of wax candles. Candle sales increased 350 percent while injuries and deaths from candle related fires increased from thirteen to forty-two percent. The candle industry and the CPSC are currently working through ASTM to develop the necessary consensus standards to improve candle fire safety. The primary objective in this cooperative effort is to reduce injuries and deaths associated with candle fires.
Although there have not been standardized regulations set forth for candles, testing labs such as FTI/SEA and MTL-ACTS are actively involved in technical evaluations for candles with the National Candle Association (NCA) and/or ASTM. Candle burn testing involves stability, burn time, abnormalities, smoke/flaring, sputter, overflow, re-ignition, flame height, afterglow, external surface temperature (thermocouple), direct flame impingement, pool temperature, carbon deposit and soot emissions. Given that a wick's performance affects all these areas of testing, major improvements and focus must be directed towards advancing wick technology.
Prior candle wicks have been woven or braided for well over the last century. Such conventional wicks are woven from multiple fiber or filamentary yarns. The most commonly used yarn is cotton, although other natural fibers such as rayon, nylon or hemp have also been employed. Braided wicks are produced in various sizes, shapes and constructions to achieve the necessary performance (flame height, wax pool size, self-trimming) and process (stability, self-supporting) requirements. The appropriate wick selection for a particular candle application includes type of weave, core, size (diameter or width) and density of wick. Even though wick selection is confined to braided wicks, there are over a thousand different types of braided wicks from which to choose. Consequently, the vast options of wicks may be a disadvantage to manufacturers or consumers, adding additional costs and time spent sourcing a proper wick. Ultimately, braided wicks still have many limitations.
Limitations include the wick's aesthetic appearance, and limited design and ambiance alternatives. Although there are thousands of different types of wicks available, they all consist of a white or natural colored, single strand woven material. Additionally, braided wicks only emit a silent, vertical flame.
Another limitation with braided wicks is that they do not provide enough capillary flow to optimize the performance of today's candles. When manufacturing a braided wick, increasing the picks per inch will increase the density of the wick (i.e. reduce the yield) and thereby reduce the size of capillaries, thus reducing the potential flame height or burn rate. Conversely, reducing the picks per inch will open the braid and reduce the density of the wick (i.e. increase the yield) and thereby increase the size of capillaries, thus optimizing the flame height or burn rate. However, such an increase in yield and burn rate from conventional braided candle wicks is limited by the fact that creating a more open structure with large capillaries creates a less stable wick which changes in characteristics when subjected to the tensions of the candle manufacturing process. In addition, the smooth surface of a braid reduces the functional surface area. The small capillaries and smooth functional surface area of the braided wick make it more difficult to create the required capillary flow rate in today's natural and gel waxes as well as candles that have high amounts of additives to modify a candle's hardness, color, burn rate and aroma (i.e. stearic acid, UV inhibitors, polyethylene, scent oils and color pigments).
Furthermore, today's candles come in different shapes, sizes, and types (i.e. filled, freestanding, taper, tealight and votive), ensuing a need for advanced wick materials and structures.
With the succession of oversized and oddly shaped candles (opposed to the traditional cylinder shapes), larger wax pool size and consumption are preferred. Due to wick height standardization by ASTM (i.e. three inches), braided wicks are limited in size and density, thus resulting in limitations in wax pool size, burn rate and consumption. For example, the thicker a cylindrical wick is, the higher its flame height. And flat wicks are restricted in width (i.e. 1/32−¼ inch) due to the unsupported nature of a braided wick. Even if a “core” or stiffing agent were applied, the wick still remains too flexible. The wider and thicker the braided wick is the more unstable and hazardous it may be. Since the size of the wax pool is related to the burn rate and flame height, braided wicks typically cannot produce a large enough wax pool to consume the majority of a larger candle without compromising the standardized flame height. Characteristically, a braided wick can produce up to a three-inch diameter wax pool while maintaining a three-inch flame height.
A traditional six-inch diameter candle requires three braided wicks to maximize consumption. This results in additional manufacturing costs, irregular wax pools and potential hazards. For instance, when one wax pool spills into another, the leaking wax may create unstable flame heights and wick drowning.
Prior art shows the need to improve wick technology that allows the wick to burn for a longer period of time and consume more wax than existing wicking material. This was addressed in U.S. Pat. No. 4,790,747, whose wick comprises a single strand of tufted wire coil having a polyethylene and wax coating. One end of the coil is turned upward into a vertical section to form the lighting element and the other end of the wire is wound into a circular base such that it touches the base of the vertical section. Consequently, the wire core technology is manufactured with braided cotton or cotton-like material, generating the same analogous performance complications as disclosed.
One category of braided wicks is “self-trimming” or flat wicks (i.e. wicks that curl or bend to the outside of the flame). Although “self-trimming” wicks may reduce afterglow, they may curl to the point where the terminal ends bend into the wax pool or continue to curl into a spiral curl. This undesirable result can cause a self-trimming braided wick to increase in length so as to increase the amount of wick material, or functional surface area, above the melted wax pool, thereby producing a continually increasing (i.e. unstable) flame height and wax pool. Conversely, it is important that a wick does not over-curl or bend to the point were the wick end touches the wax pool, causing the wick to extinguish and drown in molten wax. Consequently to re-ignite the candle, the wick needs to be located and “dug out” since the wax may cool and harden over the wick. The flat wicks are unsupported and very flexible.
The alternative category of braided wicks is “self-supporting” wicks. Self-supporting wicks (i.e. “cored wicks”) are typically round in profile and use paper, cotton, metal or polyethylene fiber material in the core of the braid to stiffen the wick. Additionally, a stiffening agent such as wax-insoluble polymer or copolymer that depolymerizes or pyrolyzes may be used to support a flaccid wick. Although many core or stiffing devices are used, braided wicks remain flexible.
Due to the flexibility in supported or unsupported woven wicks, several hazards can occur. The majority of household candle fires are the result of a candle wick leaning to one side or another in filled or freestanding candles. Filled candles with flexible wicks, particularly those enclosed in plastic or glass containers, may overheat or contact the side of the container, causing breakage or other damage. Additionally, unsupported wicks may extinguish themselves, falling into the pool of molten wax. Further, freestanding candles with an unsupported wick may incur wax spillage due to a decentralized or irregular shaped wax pool.
Certain “self-supporting” wicks may consist of toxic core materials. In April 2003, the Consumer Product Safety Commission (CPSC) banned the manufacture and sale of lead-cored wicks and candles with lead-cored wick because they could present a lead poisoning hazard to young children. This ban became effective in October 2003. The federal ban applies to all domestic and imported candles and will allow the CPSC to seek penalties for violations of the ban. Unfortunately, it is very difficult for consumers to tell if the braided “cored wicks” contain lead.
An additional obstacle with prior art wicks involves keeping a braided candle wick trimmed to a ¼ inch length for proper burning, as recommended by ASTM, NCA and most candle manufacturers and testing labs. If a braided wick is not trimmed properly, carbon balls, excessive soot emissions and fire hazards may occur. Candle manufacturers are not required and usually do not distribute a finished candle with a recommended wick size of ¼ inch.
Also, due to the nature of cotton-like material and especially “self-supporting” core material, a cutting device is needed to trim the braided wick. If a wick is positioned deep in a narrow candle jar or container, it may become difficult for conventional scissors or cutting device to trim off the excess long wick from the candle. Still, another problem is the difficulty to accurately measure a wick to the exact recommended ¼ inch length.
The primary obstruction of prior candle wicks is the emanation of excessive soot developments, resulting in smoke emission and carbon build up. Excessive soot occurs when a candle is burning as a result of the remains of carbon particles that have not been completely decomposed (burned) within the candle flame. Soot will either fully combust and burn off, released into the atmosphere as smoke, or grow into a carbon head or ball, otherwise known as “mushrooming” or “afterglow”. Furthermore, carbon heads can detach from the wick and fall into the pool of liquid fuel, where they accumulate. In addition to creating a polluted looking candle, the liquid fuel may combust, thereby igniting the carbon heads, which become hot enough to vaporize and re-ignite resulting in “flashover.” In freestanding candles, the carbon heads may heat up the wax and burn through the sides and bottom of the candle causing severe damage and fire hazards. In addition, the development of carbon heads (i.e. “afterglow”) causes the emission of unwanted smoke or toxic fumes to linger for several minutes after being extinguished.
As a result of an increase in safety requirements and environmental issues, a Smoke Test Method Task Group, formed by ASTM, developed a method to assess the propensity of a candle to smoke. Candle manufacturers and testing labs can use a simple test to measure the smoke from a candle while it is burning that allows them to improve the performance of that candle. The standard test method was recently balloted in January 2003, and the task group will continue to work toward a final standard based on the ballot results.
In today's candles a wick sustainer is primarily used to provide lateral support to a wick in a candle to hold the wick in place during pouring of the wax-like material in a container or mold or to laterally support the wick when the hardened wax liquefies, no longer supporting the braided wick. During the manufacturing of filled candles the wick is usually centrally positioned in the bottom of a container with an adhesive to seal the wick sustainer to the bottom. Many wick sustainers are difficult though to position centrally. Additionally, many wick sustainers are made of materials that are not heat resistant or have “self-extinguish” qualities resulting in the overheating of glass causing severe damage, such as by fracturing or cracking. Furthermore, the design of a wick sustain can either amplify or reduce the risk of “flashover.” A variety of wick holders for braided wick technology have been designed over the past decade or so to reduce fire hazards and increase safety. See, e.g., U.S. Pat. Nos. 1,226,850; 1,267,968; 1,309,545; 1,320,109; 1,344,446; 1,505,092; 2,291,067; 2,324,753; 3,462,235; 3,998,922; and 4,381,914.
It is known in the art to manufacture “freestanding” candles by molding, and wherein a candle body is molded by casting the wax in a mold having a wick inserted therein. Maintaining the wicks centrally in the mold during such operation is a rather difficult procedure, due to the flexibility of braided wicks. For example, as molten wax cools, it shrinks, causing wick repositioning, which increases the risk of wax spillage as the candle burns.